For example, ITU-T G.8032/Y.1344 (February 2012) (Non-Patent Document 1) describes process contents at the time of recovery from fault in the ring network based on the ITU-T G.8032. Specifically, one of two ring ports controlled to a block state with a fault link interposed therebetween is controlled to an open state based on the priority of two nodes having the two ring ports.